The blonde beauty served her spouse with divorce papers last month but her 'Hills' co-star held off signing documents confirming he had received them until August 13.
According to Californian law, Heidi will have to wait six months from that date before the divorce can be completed - meaning their marriage will not legally be over until the traditional romantic day for couples next year.
Heidi married 27-year-old Spencer in April 2009, separating 15 months later, with the 23-year-old star citing irreconcilable differences as the reason for their split.
Spencer - who is believed to have deliberately chosen the date he signed the documents - recently admitted he and Heidi had gone their separate ways because she wanted to enjoy married life out of the spotlight, while he had his sights set on increasing his fame.
He said: "We love each other but I'm a famew***e and I'll never grow out of it. Heidi knows that and doesn't want that.
"I want every kind of press. She believes in bad press. There's no way my love for fame and her love for puppies will every work out successfully. She just wants to hike and hang out and be calmer.